What is the Best Glue For Segmented Turning
You may know of us already and are aware that we use segmented turning to create our floor vases. If not, then welcome.
We use this technique as it allows us to design products that are not possible in solid wood turning at least in a consistent manner, and approaching these vases from a business perspective demands reliability and effectiveness.
While selling our products at many markets we have been asked often about the glue we use and the process of segmented turning. We can’t be with you to explain our process so we have decided to share it online for all. This article is just about glue selection.
It’s probably worth a quick visit to the front page of our website for context to this post.
It takes time, study and practice to understand the forces at play when two or more pieces of wood are joined together using glue. It is a necessary thought process to determine the end use of the item and the expected climatic conditions the item will be subjected to and it is good practice to plan out the project before any wood is dressed, cut, or turned and this includes considering what glue is best for segmented turning, as this is the topic at hand.
When choosing the best glue to use in segmented turning we advise you to consider
The type of wood and its acceptance to take glue.
The sizes of the individual segments.
The physical size of your planned segmented turning.
The possible climatic factors that the piece could be subjected to when complete.
The available time for glue-up. Your glue choice should give you time to clamp in place before it sets.
The VOC levels need to be known and compensated for.
The clamping methods available are suitable. Some glues demand very tight joints to be effective where others have gap filling abilities.
The items potential to be in contact with food.
The finish to be applied as this acts as a moisture barrier.
The clamping methods you will employ should match the requirements of the glue that is applicable to your segmented turning project.
More clamps are better than just enough and the end result will benefit greatly if the appropriate clamping tools and methods are used.
Sometimes you have to be creative (which really is just a part of woodwork anyway) and it can get interesting when you don’t have what you need available. You make things as you go.
A good example of this is the image below of the clamps on a floor vase. You should notice the ledge we left available as a clamping point as we had run out of clamp length.
The risks that turning glued pieces can attract need to be addressed.
- Operator risk while turning on the lathe. The integrity of the glue joints is vital.
- VOC levels and effects of skin contact with glue. Masks and gloves should be used as per safety data sheets of the chosen glue.
- End user risk; product longevity. The object needs to perform as expected for its service life.
- Environments risks associated with cleanup.
We have a list of the common glue types below. To filter what glue is best for your situation you should consider the lists above and match the attributes of the glue to the task.
T1 is an aliphatic resin , or carpenters glue.
T2 is a crosslinking PVA
T3 is a polymer
Technical link here
Polyvinyl acetate is a type of aliphatic resin similar to titebond 1
Some woods perform poorly with this glue. Very stiff joint.
Susceptible to moisture
Very good. Has health risks during application. Can be difficult to obtain.
Can be used in humid environments during construction. Slight gap filling abiity.
Very stiff glue, poor choice for segmented turning if venturing into larger objects. Has been used in segmented pen turning with some success.
The elephant in the room is moisture and this should be considered on two fronts.
The first is the moisture content of the wood you intend to use and the second is environmental moisture once the project is completed.
The accepted level for moisture content for segmented turning is 12-15% and most of the glue manufacturers formulate their product and do extensive testing at or around those levels; so to achieve reliable outcomes it is recommended that you abide by the guidelines for consistency.
Environmental moisture is mostly out of your hands and the best you can do is try to mitigate the potential for damage from this vector. When choosing the glue, consider using a type that has a small degree of flexibility after curing. PVA glues have this attribute however a crosslinking PVA is better than basic yellow glue.
If you expect movement from environmental moisture you might want to consider avoiding rigid glues like epoxy and similar as it is not the moisture levels that cause the damage to the joints but the cycling of moist to dry to moist and back again. This can cause fatigue in the joint and eventually it may let go.
If the environment is constant then the choice of glue is far simpler.
A good study on the effects of moisture on wood is linked here.
Here is a snippet
“Moisture is arguably the most important factor affecting the performance and service life of wood and wood products. Moisture affects the dimensional movement of wood and wood products; under certain conditions, moisture change can result in major dimensional change.”
As you put your project into action consider the end grain issues with your glue.
End grain is never a good option for any glue but should hold if careful until you have some side grain stability to help support the joint.
When we glue a layer and segments we apply two coats to the endgrain cuts. The first disappears into the grain and really does nothing but allow the secound coat to sit on the surface longer for clamping.
We recognise that this is a weak joint and treat the component once cured accordingly.
Some woods have an oily surface when cut and require a wipe with a solvent prior to gluing. We use a methylated spirits as it cleans up and evaporates quickly.
Have a cleaning agent sit for too long may weaken the integrity of any existing glue joint in certain circumstances.
While the gluing stages are underway, follow the recommended curing times as stated on the containers. Clamping during construction is mandatory for all glues but some demand very close joints to perform as advertised.
If there are any doubts on a particular joint, we recommend that it be sorted out before glue is applied. Re-cut or replace the segment to avoid issues
We will add a day or so to certain jobs just for the sleep-at-night factor and there is a good reason for this.
In our case, we turn our vases mounted only on a faceplate. We don’t use a tailstock and if you visit our home page you will see the size of our vases. We rely totally on the connection provided by glue.
Having said that, the size of the work piece also plays a part in glue choice. The bigger the project the more imperative it is to get the glue choice right. The stresses of spinning a vase with it mounted just on a faceplate are extreme so a good glue choice is a must. Our example shows the importance of the joints between segments needing to be tight and accurate so the glue can perform as demanded.
So to finish up, to successfully undertake and complete a segmented project you must understand the forces and dynamics involved during the glue-up stage, the turning stage, and then also consider the future risks from movement that the finished product will face. Get all of this sorted out before you start and you are well on the way to adding a wonderful skill to your collection.
Just for the record, we use titebond 3.
Article written by Tim Blanch as part owner of Pickers Ridge Hardwood Designs. He is a qualified Carpenter/Joiner and has been turning for over 25 years.